Abstract

The composition of milk fat from dairy cows is related to both genetic and environmental factors. Here, the effect of feed and herd was examined in 3 Scandinavian breeds, namely Danish Holstein-Friesian (DH), Danish Jersey (DJ), and Swedish Red (SR). In total, milk samples from 1,298 cows kept in indoor housing systems were collected from 61 conventional dairy herds in Denmark and Sweden. The fatty acid (FA) composition of milk was determined by gas chromatography and the content of alpha-tocopherol by HPLC. Based on the 17 individual FA determined, distinct FA profiles were observed for all breeds using univariate and multivariate statistics. The DJ cows were characterized by higher levels of saturated short-chain FA; in contrast, DH cows had higher content of unsaturated C18 FA, whereas higher levels of primarily C14:0, C14:1, C18:1 cis-9, and C18:3n-3 were evident in SR cows. This variation in milk fat composition across breeds was further reflected in different desaturase indices, which were generally higher in SR cows. In addition, alpha-tocopherol differed significantly among breeds, with DJ cows having the highest content. Herd-specific feeding plans were collected, and different feed items were separated into 4 broad feed categories, including grass products, maize silage, grain, and concentrate. The pronounced differences in overall feed composition among breeds were, to a large extent, due to regional differences between countries, with SR receiving higher levels of grain and grass silage compared with the Danish breeds. Within breeds, differences in feeding regimens among herds were furthermore higher in SR. Significant correlations between feed category and individual FA were observed in all breeds. Furthermore, variance components were estimated and used to determine the proportion of phenotypic variation that could be explained by herd. The herd effect for individual FA was generally lower for DH compared with the 2 other breeds. In addition, very low herd effects were shown for C14:1 and C16:1 in all breeds, suggesting that the content of these FA is mainly genetically regulated.